fix(agentos): answer runtime requests from every child of a WebAssembly shell

[eersnington]

Fixes #2012.

• Under a WebAssembly parent such as sh, the process pump claimed supervisor-owned events only from JavaScript children. A Python child never got its filesystem requests answered, and a nested shell never got its child_process.spawn answered. So sh -c 'python3 -c "…"', echo … | python3 -, and sh -c "sh -c 'cat f'" hung with no output.
• The pump now claims those events from children of every runtime: process-control requests, completions, Python filesystem requests and socket completions, and signal-state updates. Stdout, stderr, and exit delivery stay with the parent's child_process.poll.
• Adds shell_children_of_every_runtime_run_to_completion to crates/client/tests/process_e2e.rs. It runs Python, piped Python, a Python exit status, and a nested shell through one sh.
• Same root cause as fix(native-sidecar): keep queued child services progressing beneath WASM parents #2013 and the nested-shell case in fix: service queued process-control RPCs beneath WASM parents #2007. This change keeps the fix to the pump's admission check.

[railway-app]

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[the-company-company]

🔴 1 high-severity finding

_{Reviewed commit d4a62c7.}

[the-company-company]

🔴 High · Probe empty non-JavaScript child queues

A Python child’s first VFS request is still in its runtime event receiver, so pending_execution_events.front() is None here and this returns false. The WASM-parent branch then continues without calling try_poll_execution_event; if the parent reaches child_process.poll first, that same request is polled without owned_python_services and fails with ERR_AGENTOS_PYTHON_EVENT_OWNERSHIP instead of being serviced. This leaves the Python-under-shell path added by the E2E test dependent on a queue state that normal runtime events do not create. Probe children of every runtime when this queue is empty (for example, let the existing preserving nowait poll run for None) so Python VFS requests and WASM internal RPCs can be discovered and claimed.

[eersnington]

slop. prod's dispatcher uses poll_owned_descendant_javascript_child_process which

1. reads the python request
2. queues it for the supervisor
3. calls notify_one()

the shell queues the py req, and this fix handles it. this is looking at the wrong code path